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124 lines
3.0 KiB
C
124 lines
3.0 KiB
C
/* sem_wait -- wait on a semaphore. Generic futex-using version.
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Copyright (C) 2003-2014 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <sysdep.h>
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#include <lowlevellock.h>
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#include <internaltypes.h>
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#include <semaphore.h>
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#include <pthreadP.h>
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#include <shlib-compat.h>
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#include <atomic.h>
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void
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attribute_hidden
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__sem_wait_cleanup (void *arg)
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{
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struct new_sem *isem = (struct new_sem *) arg;
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atomic_decrement (&isem->nwaiters);
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}
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/* This is in a seperate function in order to make sure gcc
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puts the call site into an exception region, and thus the
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cleanups get properly run. */
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static int
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__attribute__ ((noinline))
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do_futex_wait (struct new_sem *isem)
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{
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int err, oldtype = __pthread_enable_asynccancel ();
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err = lll_futex_wait (&isem->value, 0, isem->private ^ FUTEX_PRIVATE_FLAG);
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__pthread_disable_asynccancel (oldtype);
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return err;
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}
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int
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__new_sem_wait (sem_t *sem)
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{
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struct new_sem *isem = (struct new_sem *) sem;
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int err;
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if (atomic_decrement_if_positive (&isem->value) > 0)
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return 0;
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atomic_increment (&isem->nwaiters);
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pthread_cleanup_push (__sem_wait_cleanup, isem);
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while (1)
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{
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err = do_futex_wait(isem);
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if (err != 0 && err != -EWOULDBLOCK)
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{
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__set_errno (-err);
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err = -1;
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break;
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}
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if (atomic_decrement_if_positive (&isem->value) > 0)
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{
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err = 0;
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break;
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}
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}
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pthread_cleanup_pop (0);
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atomic_decrement (&isem->nwaiters);
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return err;
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}
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versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);
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#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
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int
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attribute_compat_text_section
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__old_sem_wait (sem_t *sem)
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{
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int *futex = (int *) sem;
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int err;
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do
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{
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if (atomic_decrement_if_positive (futex) > 0)
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return 0;
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/* Enable asynchronous cancellation. Required by the standard. */
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int oldtype = __pthread_enable_asynccancel ();
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/* Always assume the semaphore is shared. */
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err = lll_futex_wait (futex, 0, LLL_SHARED);
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/* Disable asynchronous cancellation. */
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__pthread_disable_asynccancel (oldtype);
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}
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while (err == 0 || err == -EWOULDBLOCK);
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__set_errno (-err);
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return -1;
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}
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compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);
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#endif
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